Selective Stalling of Human Translation by Small Molecules

摘要 许多人类疾病的蛋白质靶标由于其潜在的生化行为而仍然是“无法下药的”。 发现小分子药物的这些限制阻碍了开发负担得起的疗法的希望。 在这里，我们建议开发一种全新的行动机制，它可以使以前的目标 “不能下药的”蛋白质，通过选择性地阻止人类核糖体的翻译。大多数药物和药物 已知可调节人类翻译靶向翻译起始因子复合体或上游的候选 哺乳动物雷帕霉素靶标(MTOR)等信号通路。这些通常调整翻译的 大量的mRNA。到目前为止，只有一种类型的化合物选择性地靶向核糖体-诱导 提前终止密码子通读-正在临床上进行评估。我们最近展示了一个小的 分子可以选择性地拖延人类蛋白质的翻译，几乎没有偏离目标的活性。这个 我们分析的化合物PF-06446846(PF846)直接和选择性地抑制PCSK9的翻译 在翻译延伸过程中，通过使位于核糖体出口的新生多肽上的核糖体停滞 隧道。然而，目前还不清楚这种化合物和相关化合物是如何选择性地阻碍翻译的。为数不多的 我们发现的被PF846抑制的脱靶蛋白的例子(不到人类的0.4% 蛋白质组)表现出很大的一级结构变异性，使得预测目标序列变得困难 选择性核糖体靶向药物的未来发展。我们有初步证据表明，PF846与 这些不同的新生链序列通过微妙的不同机制诱导核糖体停滞。我们 建议阐明PF846翻译停滞的全分子机制，从而使这一家族 化合物可以进一步优化以靶向其表达或过度表达导致不同 目前尚无治疗方法的人类疾病。这一系列化合物也可以进行优化 以病毒为目标，这些病毒使用人类翻译来合成它们的蛋白质组。这些努力有可能 为人类治疗发展开辟了一种全新的作用机制。

ABSTRACT Protein targets for many human diseases remain “undruggable” due to their underlying biochemical behavior. These limits to discovery of small molecule drugs hold back the promise of developing affordable therapeutics. Here we propose to develop an entirely new mechanism of action that could enable targeting previously “undruggable” proteins, by selectively blocking their translation by the human ribosome. Most drugs and drug candidates known to modulate human translation target translation initiation factor complexes or upstream signaling pathways such as mammalian target of Rapamycin (mTOR). These generally modulate translation of a large number of mRNAs. To date, only one type of compound that selectively targets the ribosome–to induce premature stop codon readthrough–is being evaluated in the clinic. We recently demonstrated that small molecules can selectively stall the translation of human proteins, with very little off-target activity. The compound we analyzed, PF-06446846 (PF846), directly and selectively inhibits the translation of PCSK9 during translation elongation, by stalling the ribosome on the nascent polypeptide residing in the ribosome exit tunnel. However, it remains unclear how this and related compounds selectively stall translation. The few examples of off-target proteins we identified as stalled by PF846 (less than 0.4 percent of the human proteome) exhibit substantial primary structure variability, making it difficult to predict target sequences for future development of selective ribosome-targeting drugs. We have preliminary evidence that PF846 interacts with these diverse nascent chain sequences to induce ribosome stalling by subtly different mechanisms. We propose to elucidate the full molecular mechanism of PF846 stalling of translation, so that this family of compounds can be further optimized to target proteins whose expression or overexpression causes diverse human diseases for which no treatments are now available. This family of compounds could also be optimized to target viruses, which use human translation to synthesize their proteome. These efforts have the potential to open up an entirely new mechanism of action for human therapeutic development.